Terminating SWA in a buried backbox?

[Steve]

Some people feel its belts and braces. Personally its something I'd do if I was rewiring my house. Look at America, they have seperate circuits for their washers, dryers, fridges, and have done for many years. But this is for different reasons (there electrical system is far inferior to ours)

I mean, lets say your RCD trips due to a wiring fault that you cannot cure there and then and have to wait for a spark. Your boiler and fridge are in the kitchen. You dont want either of them to go off (say its winter). So then you have to unwire the boiler, put a plugtop on it, get an extension lead, run it to an unaffected circuit etc. Its a big hassle. If they werent RCD protected, it wouldnt matter.

Some people now use emergency lights on their stairwells and near the consumer units.

 

[RF Lighting]

You'd probably have some sort of heart attack if you came and saw my brothers kitchen.

There is:
a dedicated 32A radial for the washer, dryer and dishwasher.
a dedicated 32A radial for the hob
a dedicated 20A radial for the oven and extractor hood.
a dedicated 16A radial for the fridge

All these circuits have been run in flush mounted steel conduit where the wiring is concealed in the wall to avoid the need for RCD protection.

There is a ring final circuit protected by a 32A RCBO for the general sockets in there too.

I've got 3 emergency lights in my house despite the lighting not being on RCD.

 

[Donkmeister]

Thanks for all the help guys.

Steve,

it seems to be totaly mad!
...
But just feel this is OTT.

CBW

To be honest, I am a little a**l. I have never had a freezer full of food spoil due to an RCD trip, but as an RCBO + T&E costs the same as an MCB + SWA in this case, I might as well go for the less "trippable" solution. I used to be an aerospace engineer and force of habit tells me "Aha, reversionary modes, graceful degredation, remove the common failures wherever possible!!"

Looking at it in a more practical sense, even the most basic rewire will take me plenty of time and involve plenty of upheaval, so whilst I've got floorboards up and walls being chased, I might as well spend an extra hour and a few more pounds here-and-there in order to make it the best job I can within my ability and budget. I'll be taking photos and posting progress up here once I get cracking (hopefully in a couple of weeks, just need to complete and post my Building Notice).

Some people now use emergency lights on their stairwells and near the consumer units.

Add one to your tally. B-A-S suggested using a bulkhead by the CU in one of my earlier rewire threads and I've now bought my 3-hr emergency bulkhead to go in the cupboard with CU and equipment rack... I was going to put one on the landing but there is nowhere to hide one...

... so I'll probably end up buying a gear tray and equipment to power a standard landing light.

(should have seen the look on SWMBO's face when I produced the self-adhesive emergency exit stickers they supply with it!!!)

Has anyone used Flexishield? How tough is it? Looking at their website it seems to be designed more to ensure an MCB will trip if you hammer a nail through it rather than to provide actual mechanical protection.

 

[ban-all-sheds]

Are you going to supply the bulkhead through an "upside down" switch?

Anyway - can't yet claim to "add a 2nd to your tally", as they are still in boxes, but I've got 3 sustained Thorn Chalice lights waiting to go into the landing and hallway.

And I've started installing trunking and conduit for the wiring for the new kitchen which should now be going ahead next year.

 

[Donkmeister]

Are you going to supply the bulkhead through an "upside down" switch?

In the end I went for a "maintained" version that lets me turn the light on and off at will without switching to back-up power. My thinking was that I may want to have light in the cupboard for extended periods to fettle my equipment, thus I will use a two-module grid with a secret key switch to break the supply for testing/run-flat purposes, and a normal switch to turn it on and off at will.

I was concerned that secret key switches may be a hindrance a few owners down the line when no-one is bothered about what they do anyway, but then I realised that by that point DIY electrics will probably be completely illegal anyway.

 

[ban-all-sheds]

I will use a two-module grid with a secret key switch to break the supply for testing/run-flat purposes.

You don't really need that in your cupboard under your stairs, do you...

I was concerned that secret key switches may be a hindrance a few owners down the line when no-one is bothered about what they do anyway, but then I realised that by that point DIY electrics will probably be completely illegal anyway.

Won't stop it though.

 

[Steve]

Back to the topic, would the earth armour connection NEED to be accessible under plaster? If its under plaster, it cannot move and cannot loosen itself off. There is a test point for the connection visible inside the socket box - the gland itself. IMO its a permenant joint, because it mechanically cannot move.



<lights blue touchpaper>

 

[RF Lighting]

I wouldn't really be too concerned. I've never seen a SWA gland go wrong apart from the cable being wrenched out, but that obviously can't happen here.

Can't remember if you said that one end of the cable will remain exposed anyway?

Now back to the off topic bit. I have these emergency lights on the ceiling in the hallway and at the top of the stairs:

They are only about 50mm diameter, and hardly noticeable. I have them wired so they go into maintained mode if the smoke alarms go off.

I also have a posh test switch

 

[ban-all-sheds]

I wouldn't really be too concerned. I've never seen a SWA gland go wrong apart from the cable being wrenched out, but that obviously can't happen here.

Indeed not, but I think that in theory it's a connection within the scope of 526.3.

I have them wired so they go into maintained mode if the smoke alarms go off.

Wouldn't it have been simpler to get smokes with integral lights?

 

[RF Lighting]

I wouldn't really be too concerned. I've never seen a SWA gland go wrong apart from the cable being wrenched out, but that obviously can't happen here.

Indeed not, but I think that in theory it's a connection within the scope of 526.3.

Hmm good point.

I have them wired so they go into maintained mode if the smoke alarms go off.

Wouldn't it have been simpler to get smokes with integral lights?

Where would be the fun in that?

 

[holmslaw]

..

 

[ban-all-sheds]

No its not, section 526 is about electrical conductor (wire/cable) connections.

The armour is a conductor, as is the the sheath of pyro.

If you stretch that to mean any electrical connection then flush installations would not be allowed.

Why not? You can have flush installations with all of the connections accessible.

 

[ban-all-sheds]

I meant to ask

I have them wired so they go into maintained mode if the smoke alarms go off.

Do the smokes have an output for that, or did you tap into the interlink?

 

[RF Lighting]

You can get a relay module which connects to the interlink wire, and provides two pairs of volt free contacts for switching lighting / signalling etc.

 

[Donkmeister]

So, is the consensus that it is fine to use 3-core SWA, using one core for earth, and bury a weatherproof gland?

The gland at CU end of the SWA will remain accessible.

The Building Inspectors round here are only interested in structural stuff anyway, I could probably get away with a bit of bellwire just so long as I don't go too far into the brickwork

RF - I raise my hat to your industrial-grade emergency lighting installation!!!